A plasma-generating device that generates plasma using EM radiation is known. For example, JP 2007-113570A1 discloses an ignition device including such a plasma-generating device.
An ignition device described in JP 2007-113570A1 is equipped in an internal combustion engine. The ignition device generates a plasma discharge by emitting microwaves in a combustion chamber before or after the ignition of an air-fuel mixture. The ignition device produces local plasma using the discharge from an ignition plug such that the plasma is generated in a high-pressure field, and then develops this plasma using the microwaves. The local plasma is generated in a discharge gap between the tip of an anode terminal and a ground terminal.
In a conventional internal combustion engine, plasma is produced near a radiation antenna that emits EM radiation.